Various publications, including patents, published applications, technical articles and scholarly articles are cited throughout the specification. Each of these cited publications is incorporated by reference herein in its entirety.
The Notch protein family is important for cell fate determination during development and tissue homeostasis in the adult. Upon ligand engagement via the Notch ecto-domain, Notch undergoes sequential extracellular and intramembrane processing. The intra-membrane processing of Notch is mediated by γ-secretase. Cleavage of Notch by γ-secretase leads to release of the Notch intracellular domain (NICD). The NICD fragment mediates Notch signaling via translocation to the nucleus, where it regulates expression of several genes. (Jarriault et al., Nature 377(6547): 355-358 (1995); Kopan et al., Proc Natl Acad Sci USA 93(4):1683-1688 (1996); Schroeter et al., Nature 393(6683):382-386 (1998)). In particular, Notch signaling activates transcription of the mammalian homolog of the Drosophila transcription factor hairy-enhancer of split (Hes). Transcriptional activation of Hes1 is mediated by de-repression of CBF1/RBPJk upon binding by NICD in the nucleus. A number of genes whose expression is regulated by NICD mediate cellular differentiation in many neural and non-neural tissues during development, as well as in the adult (Selkoe and Kopan, Annu. Rev. Neurosci., 26:565-597 (2003)).
γ-secretase is a multiprotein complex consisting of presenilin, nicastrin, Aph-1, and Pen-2 that cleaves several substrate proteins in addition to the Notch receptor family (e.g., Notch 1, 2, 3, and 4) including proteins of the amyloid precursor protein (APP) family (e.g., APP, APLP-1, APLP-2) and E- and N-cadherin superfamily, LRP, Nectin-1α, CD44, ErbB4, and Notch ligands including Jagged-2 and Delta-1 (DeStrooper, Neuron, 38:9-12 (2003)). The cleavage products of several γ-secretase substrates have been implicated in various disease states, including Alzheimer's Disease and cancer. Cleavage of APP by γ-secretase leads to β-amyloid (Aβ) synthesis, the major component of amyloid plaques in patients suffering from Alzheimer's disease (Id.). Additionally, Notch intracellular domain (NICD) has been linked to tumor angiogenesis (Li and Harris, Cancer Cell, 8:1-3 (2005)). Notch1 activation also has been implicated in acute T-cell lymphoblastic leukemia (Chiang and Pear, Eur. J. Hum. Genet., 13:393-398 (2005); Weng et al., Science, 306:269-271 (2004)). Notch signaling also has been linked to growth and survival of medulloblastoma cells (Hallahan et al., Canc. Res., 64:7794-7800 (2004)). Inhibition of the Notch pathway, however, has been demonstrated to induce goblet cell differentiation in adenomas in mice carrying a mutation of the Apc tumor suppressor gene (van Es et al., Nature, 435:959-963 (2005)).
Complete inhibition of γ-secretase activity has been suggested to cause severe side-effects (Selkoe and Kopan, Annu. Rev. Neurosci., 26:565-597 (2003); Doerfler et al., Proc Natl. Acad. Sci USA 98, 9312-9317 (2001); Hadland et al., Proc Natl. Acad. Sci USA 98, 7487-7491 (2001)). For example, recent studies showed that γ-secretase inhibitors cause intestinal goblet cell metaplasia in rats (Milano et al., Toxicol. Sci., 82:341-358, 2004). Reagents that selectively inhibit cleavage of a target γ-secretase substrate without affecting cleavage of other γ-secretase substrates are thus desirable. As an example, a subset of nonsteroidal anti-inflammatory drugs (NSAIDs) was shown to decrease the production of Aβ42 (Weggen et al., Nature 414:212-216, 2001), without significantly affecting γ-secretase-mediated cleavage of ErbB4 (Weggen et al., J. Biol. Chem. 278, 30748-30754, 2003). In particular, compounds which are able to selectively inhibit cleavage of a target γ-secretase substrate with no or minimal inhibition of the cleavage of Notch are attractive and promising as therapeutic reagents. For example, compounds that selectively inhibit cleavage of APP with no or minimal inhibition of Notch cleavage would be candidate compounds for treatment of Alzheimer's disease.